The present invention relates to a motor-driven compressor.
In motor-driven compressors, generally, a hermetic terminal is provided. Japanese Unexamined Patent Application Publication No. 2005-307798 discloses a hermetic terminal that is composed of a terminal base disposed in a through-hole formed in a compressor housing, a conductive member for electrically connecting an electric motor and an inverter, and an insulating member supporting the conductive member on the terminal base while insulating the conductive member from the terminal base. The conductive member is connected to a cluster block in the compressor housing. The cluster block has a terminal housing accommodating therein an electrical connecting portion that includes a connecting terminal connecting to the conductive member and an electric wire extending from the electric motor.
In such motor-driven compressors, when the operation is stopped, refrigerant gas existing in the compressor housing is cooled and condensed, and liquid refrigerant may remain in the compressor housing, accordingly. In such a case, if any part of the conductive member is soaked in the liquid refrigerant, electrical conduction between the conductive member and the compressor housing may be caused by the liquid refrigerant, and electrical insulation between the conductive member and the compressor housing may not be maintained. When the compressor is started in such condition, current supplied to the conductive member may leak to the compressor housing through the liquid refrigerant.
To prevent such current leakage, Japanese Unexamined Patent Application Publication No. 2001-182655 discloses a motor-driven compressor, according to which part of the conductive member and the insulating member in the compressor housing are covered with an insulating resin, whereby the insulation distance between the conductive member and the compressor housing is increased and the conductive member is insulated from the compressor housing.
It is suggested to seal the inside of the terminal housing from the outside thereof to prevent liquid refrigerant from entering into the terminal housing. By so doing, electrical conduction between the compressor housing and the electrical connecting portion in the terminal housing through the liquid refrigerant is prevented, and the electrical insulation therebetween is maintained, accordingly. However, since the terminal housing is hermetically closed by sealing the inside of the terminal housing from the outside thereof, the liquid refrigerant remaining in the compressor housing may cause a pressure difference between the terminal housing and the compressor housing, and the terminal housing may be damaged by the pressure difference. To reduce such pressure difference, it is suggested to form an opening in the terminal housing for fluid communication between the terminal housing and the compressor housing thereby to equalize the pressures in the terminal housing and the compressor housing. However, current supplied to the conductive member may leak to the compressor housing through any liquid refrigerant entering into the terminal housing through the opening, and electrical insulation between the compressor housing and the electrical connecting portion in the terminal housing may not be maintained.
The present invention is directed to providing a motor-driven compressor that allows the pressures in a terminal housing and a compressor housing to be equalized and also maintains electrical insulation of the compressor housing from an electrical connecting portion in the terminal housing.